doc(debugger): announce deprecation

[coryan]

This change is 

[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: 37e6934d96e37b2806763e2627e79980f52dcb5a

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[codecov]

Codecov Report

Merging #9552 (ac89cca) into main (c03a1e9) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #9552   +/-   ##
=======================================
  Coverage   94.37%   94.37%           
=======================================
  Files        1489     1489           
  Lines      137486   137486           
=======================================
+ Hits       129750   129753    +3     
+ Misses       7736     7733    -3     

Impacted Files	Coverage Δ
...cloud/pubsub/internal/subscription_session_test.cc	98.49% <0.00%> (+0.50%)	⬆️

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[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: ac89cca996d5c6d2cc87a81182e6c5a799faeeef

• Public Access Build Logs
• Cloud Build Console (requires auth)
• Kokoro Logs (requires auth)

ℹ️ NOTE: Kokoro logs are linked from "Details" below.